Processing of missing data by neural networks

We propose a general, theoretically justified mechanism for processing missing data by neural networks. Our idea is to replace typical neuron's response in the first hidden layer by its expected value. This approach can be applied for various types of networks at minimal cost in their modification. Moreover, in contrast to recent approaches, it does not require complete data for training. Experimental results performed on different types of architectures show that our method gives better results than typical imputation strategies and other methods dedicated for incomplete data

Effect of smoking on lung function, respiratory symptoms and respiratory diseases amongst HIV-positive subjects: a cross-sectional study

<p>Abstract</p> <p>Background</p> <p>Smoking prevalence in human immunodeficiency virus (HIV) positive subjects is about three times of that in the general population. However, whether the extremely high smoking prevalence in HIV-positive subjects affects their lung function is unclear, particularly whether smoking decreases lung function more in HIV-positive subjects, compared to the general population. We conducted this study to determine the association between smoking and lung function, respiratory symptoms and diseases amongst HIV-positive subjects.</p> <p>Results</p> <p>Of 120 enrolled HIV-positive subjects, 119 had an acceptable spirogram. Ninety-four (79%) subjects were men, and 96 (81%) were white. Mean (standard deviation [SD]) age was 43.4 (8.4) years. Mean (SD) of forced expiratory volume in one second (FEV₁) percent of age, gender, race and height predicted value (%FEV₁) was 93.1% (15.7%). Seventy-five (63%) subjects had smoked 24.0 (18.0) pack-years. For every ten pack-years of smoking increment, %FEV₁decreased by 2.1% (95% confidence interval [CI]: -3.6%, -0.6%), after controlling for gender, race and restrictive lung function (R²= 0.210). The loss of %FEV₁in our subjects was comparable to the general population. Compared to non-smokers, current smokers had higher odds of cough, sputum or breathlessness, after adjusting for highly active anti-retroviral therapy (HAART) use, odds ratio OR = 4.9 (95% CI: 2.0, 11.8). However respiratory symptom presence was similar between non-smokers and former smokers, OR = 1.0 (95% CI: 0.3, 2.8). All four cases of COPD (chronic obstructive pulmonary disease) had smoked. Four of ten cases of restrictive lung disease had smoked (p = 0.170), and three of five asthmatic subjects had smoked (p = 1.000).</p> <p>Conclusions</p> <p>Cumulative cigarette consumption was associated with worse lung function; however the loss of %FEV₁did not accelerate in HIV-positive population compared to the general population. Current smokers had higher odds of respiratory symptoms than non-smokers, while former smokers had the same odds of respiratory symptoms as non-smokers. Cigarette consumption was likely associated with more COPD cases in HIV-positive population; however more participants and longer follow up would be needed to estimate the effect of smoking on COPD development. Effective smoking cessation strategies are required for HIV-positive subjects.</p

A comparison of the MOS-HIV and SF-12v2 for measuring health-related quality of life of men and women living with HIV/AIDS

BACKGROUND: The purpose of this study was to examine the relationship between the Medical Outcomes Study-HIV Health Survey (MOS-HIV) and the SF-12v2 to determine if the latter is adequate to assess the health-related quality of life (HRQoL) of men and women living with HIV/AIDS. 112 men and women living with HIV/AIDS who access care at a tertiary HIV clinic in Hamilton, Ontario were included in this cross-sectional analysis. Correlation coefficients of the MOS-HIV physical and mental health summary scores (PHS and MHS) and the SF-12v2 physical and mental component summary scales (PCS and MCS) were calculated along with common sub-domains of the measures including physical functioning (PF), bodily pain (BP), general health perceptions (GH), vitality (VT), social functioning (SF) and mental health (MH) to explore the relationship between these two HRQoL measures. The sub-domains role physical (RP) and role emotional (RE) of the SF-12v2 were compared separately to the sub-domain role functioning (RF) of the MOS-HIV. Weighted kappa scores were calculated to determine agreement beyond chance between the MOS-HIV and SF-12v2 in assigning a HRQoL state (i.e. low, moderate, good, very good). RESULTS: The MOS-HIV had mean PHS and MHS summary scores of 47.3 (SD = 11.5) and 49.2 (SD = 10.7) respectively. The mean SF-12v2 PCS and MCS scores were 47.7 (SD = 11.0) and 44.0 (SD = 10.4). The MOS-HIV and SF-12v2 physical and mental health summary scores were positively correlated (r = 0.84, p < 0.001 and r = 0.76, p < 0.001). All common sub-domains were significantly correlated at p values from < 0.001 to 0.034. Substantial agreement was observed in assigning a HRQoL state (Physical: κ = 0.788, SE = 0.095; Mental: κ = 0.707, SE = 0.095). CONCLUSIONS: This analysis validates the SF-12v2 for measuring HRQoL in adult men and women living with HIV/AIDS

Smoking, season, and detection of chlamydia pneumoniae DNA in clinically stable COPD patients

BACKGROUND: The prevalence and role of Chlamydia pneumoniae in chronic obstructive pulmonary disease (COPD) remain unclear. METHODS: Peripheral blood mononuclear cells were obtained from 100 outpatients with smoking-related, clinically stable COPD, and induced sputum was obtained in 62 patients. RESULTS: Patients had mean age (standard deviation) of 65.8 (10.7) years, mean forced expiratory volume in one second of 1.34 (0.61) L, and 61 (61.0%) were male. C. pneumoniae nucleic acids were detected by nested polymerase chain reaction in 27 (27.0%). Current smoking (odds ratio {OR} = 2.6, 95% confidence interval {CI}: 1.1, 6.6, P = 0.04), season (November to April) (OR = 3.6, 95% CI: 1.4, 9.2, P = 0.007), and chronic sputum production (OR = 6.4, 95% CI: 1.8, 23.2, P = 0.005) were associated with detection of C. pneumoniae DNA. CONCLUSIONS: Prospective studies are needed to examine the role of C. pneumoniae nucleic acid detection in COPD disease symptoms and progression

Association of circulating Chlamydia pneumoniae DNA with cardiovascular disease: a systematic review

BACKGROUND: Chlamydia pneumoniae antigens, nucleic acids, or intact organisms have been detected in human atheroma. However, the presence of antibody does not predict subsequent cardiovascular (CV) events. We performed a systematic review to determine whether the detection of C. pneumoniae DNA in peripheral blood mononuclear cells (PBMC) was associated with CV disease. METHODS: We sought studies of C. pneumoniae DNA detection in PBMC by polymerase chain reaction (PCR) among patients with CV disease or other clinical conditions. We pooled studies in which CV patients were compared with non-diseased controls. We analyzed differences between studies by meta-regression, to determine which epidemiological and technical characteristics were associated with higher prevalence. RESULTS: Eighteen relevant studies were identified. In nine CV studies with control subjects, the prevalence of circulating C. pneumoniae DNA was 252 of 1763 (14.3%) CV patients and 74 of 874 (8.5%) controls, for a pooled odds ratio of 2.03 (95% CI: 1.34, 3.08, P < 0.001). Prevalence was not adjusted for CV risk factors. Current smoking status, season, and age were associated with C. pneumoniae DNA detection. High prevalence (>40%) was found in patients with cardiac, vascular, chronic respiratory, or renal disease, and in blood donors. Substantial differences between studies were identified in methods of sampling, extraction, and PCR targets. CONCLUSIONS: C. pneumoniae DNA detection was associated with CV disease in unadjusted case-control studies. However, adjustment for potentially confounding measures such as smoking or season, and standardization of laboratory methods, are needed to confirm this association

Mobile phone text messages for improving adherence to antiretroviral therapy (ART): a protocol for an individual patient data meta-analysis of randomised trials

IntroductionMobile phone text messaging is emerging as an important tool in the care of people living with HIV; however, reports diverge on its efficacy in improving adherence to antiretroviral therapy (ART), and little is known about which patient groups may benefit most from phone-based adherence interventions. We will conduct an individual patient data meta-analysis to investigate the overall and subgroup effects of text messaging in three recently published text-messaging randomised controlled trials.Methods and analysisData from two Kenyan and one Cameroonian trial will be verified, reformatted and merged. We will determine pooled effect sizes for text messaging versus standard care for improving adherence to ART using individual patient random-effects meta-analysis. We will test for the interaction effects of age, gender, level of education and duration on ART. Sensitivity analyses will be conducted with regard to thresholds for adherence, methods of handling missing data and fixed-effects meta-analysis. Only anonymised data will be collected from the individual studies.Ethics and disseminationEthical approval was obtained for the individual studies. The results of this paper will be disseminated as peer-reviewed publications, at conferences and as part of a doctoral thesis. This individual patient data meta-analysis may provide important insights into the effects of text messaging on ART adherence in different subpopulations, with important implications for programme implementation involving such interventions and future research

Mobile phone text messages for improving adherence to antiretroviral therapy (ART): an individual patient data meta-analysis of randomised trials

ObjectivesOur objectives were to analyse the effects of text messaging versus usual care in improving adherence to antiretroviral therapy (ART) in people living with HIV using individual patient data meta-analysis. Adjusted, sensitivity and subgroup analyses were conducted.Setting3 randomised controlled trials conducted between 2010 and 2012 in rural and urban centres in Cameroon and Kenya (two studies) were used.ParticipantsA total of 1166 participants were included in this analysis (Cameroon=200; Kenya=428 and 538).Primary and secondary outcomesThe primary outcome was adherence to ART >95%. The secondary outcomes were mortality, losses to follow-up, transfers and withdrawals.ResultsText messaging improved adherence to ART (OR 1.38; 95% CIs 1.08 to 1.78; p=0.012), even after adjustment for baseline covariates (OR 1.46; 95% CI 1.13 to 1.88; p=0.004). Primary education (compared with no formal education) was associated with a greater intervention effect on adherence (OR 1.65; 95% CI 1.10 to2.48; p=0.016) and also showed a significant subgroup effect (p=0.039). In sensitivity analysis, our findings were robust to a modified threshold of adherence, multiple imputation for missing dataand aggregate level data pooling, but not to fixed-effects meta-analyses using generalised estimation equations. There was a significant subgroup effect for long weekly (p=0.037), short weekly text messages (p=0.014) and interactive messaging (p=0.010). Text messaging did not significantly affect any of the secondary outcomes.ConclusionsText messaging has a significant effect on adherence to ART, and this effect is influenced by level of education, gender, timing (weekly vs daily) and interactivity. We recommend the use of interactive weekly text messaging to improve adherence to ART, which is most effective in those with at least a primary level of education